The bank monitored the sound and it was very loud, a source familiar with the system told us. “It was as high as their equipment could monitor, over 130dB”.

Sound means vibration, and this is what damaged the hard drives. The HDD cases started to vibrate, and the vibration was transmitted to the read/write heads, causing them to go off the data tracks. “The inert gas deployment procedure has severely and surprisingly affected several servers and our storage equipment,” ING said in a press release.

There is still very little known about how sound can cause hard drive failure. One of the first such experiments was made by engineer Brendan Gregg, in 2008, while he was working for Sun's Fishworks team. He recorded a video in which he explains how shouting in a data center can result in hard drives malfunction.